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Peach Mountain Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Peach Mountain Observatory clear sky chart from 2005-11-05 to 2017-09-10.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
37%
15864
15%
46857
10%
15822
42%
15822
20%
32724

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
16%
900
10%
2506
4%
895
22%
895
12%
1990
January16th to endNight
20%
873
8%
2601
3%
873
24%
873
11%
2079
February1st to 15thNight
17%
701
9%
2244
3%
701
23%
701
10%
1735
February16th to endNight
25%
631
14%
1893
5%
631
33%
631
15%
1377
March1st to 15thNight
27%
720
14%
2088
8%
720
32%
720
17%
1516
March16th to endNight
32%
768
18%
2112
10%
768
39%
768
21%
1481
April1st to 15thNight
29%
572
13%
1808
7%
572
35%
572
18%
1264
April16th to endNight
35%
540
19%
1620
8%
540
45%
540
24%
1086
May1st to 15thNight
36%
540
14%
1620
8%
540
42%
540
21%
1131
May16th to endNight
50%
562
15%
1663
11%
561
55%
561
28%
1064
June1st to 15thNight
56%
540
14%
1440
11%
540
60%
540
32%
920
June16th to endNight
58%
540
17%
1440
12%
540
63%
540
34%
919
July1st to 15thNight
66%
510
16%
1360
13%
510
68%
510
39%
824
July16th to endNight
68%
564
19%
1489
15%
531
71%
531
40%
875
August1st to 15thNight
67%
539
20%
1609
16%
536
70%
536
35%
957
August16th to endNight
65%
573
22%
1758
18%
573
68%
573
33%
1044
September1st to 15thNight
58%
637
25%
1862
20%
637
62%
637
35%
1091
September16th to endNight
59%
657
23%
1815
17%
657
62%
657
33%
1130
October1st to 15thNight
46%
660
20%
1886
16%
660
50%
660
26%
1247
October16th to endNight
26%
704
14%
2216
9%
704
35%
704
17%
1561
November1st to 15thNight
35%
700
19%
2276
16%
700
41%
700
22%
1472
November16th to endNight
25%
720
13%
2340
9%
720
31%
720
14%
1717
December1st to 15thNight
19%
753
8%
2523
4%
753
23%
753
10%
1969
December16th to endNight
15%
960
8%
2688
1%
960
21%
960
8%
2275

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
14%8%47%6%35%45%7%33%
47753
Night
15%8%36%5%34446%35%
47034
Cloud CoverDay
14%8%46%6%35%45%7%32%
47763
Night
15%8%36%5%34446%35%
47038
TransparencyDay
49%6%11%19%11%1
47448
Night
48%5%12%20%11%1
46857
SeeingDay
16%7%27%24%16%7%
5839
Night
18%8%28%29%13%1
15868

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
17%16%6%9%8%45%436%17%
1432
16th to endDay
16%16%8%10%9%45%44415%
1620
February1st to 15thDay
15%13%7%12%8%35%445%19%
1616
16th to endDay
15%12%6%11%8%35%35%6%20%
1580
March1st to 15thDay
16%12%47%5%35%35%6%27%
1861
16th to endDay
18%9%48%5%34446%30%
2112
April1st to 15thDay
19%10%36%5%3445%6%30%
2148
16th to endDay
17%7%26%5%24347%38%
2340
May1st to 15thDay
19%8%36%5%35%446%31%
2331
16th to endDay
13%6%25%5%35%45%7%39%
2449
June1st to 15thDay
10%5%25%5%35%5%5%8%39%
2520
16th to endDay
9%435%6%46%6%7%10%34%
2520
July1st to 15thDay
7%5%245%35%5%6%9%44%
2520
16th to endDay
8%425%6%36%6%7%9%39%
2577
August1st to 15thDay
8%6%26%6%35%6%5%8%39%
2340
16th to endDay
10%6%35%5%35%5%6%9%38%
2441
September1st to 15thDay
12%426%5%4445%7%41%
1974
16th to endDay
11%6%245%445%6%9%39%
1815
October1st to 15thDay
14%7%26%5%35%447%38%
1744
16th to endDay
20%9%36%6%34346%31%
1653
November1st to 15thDay
14%8%36%5%25%45%6%38%
1582
16th to endDay
18%12%46%6%35%45%5%27%
1620
December1st to 15thDay
15%14%7%10%6%345%46%21%
1422
16th to endDay
20%16%8%11%7%3343415%
1536
January1st to 15thNight
22%12%5%8%6%3435%5%23%
2506
16th to endNight
13%12%8%11%8%5%5%436%20%
2601
February1st to 15thNight
15%14%5%8%6%35%335%26%
2242
16th to endNight
15%10%5%9%5%3445%6%28%
1893
March1st to 15thNight
17%10%45%6%34446%32%
2076
16th to endNight
15%8%35%5%35%45%8%34%
2112
April1st to 15thNight
18%8%345%35%5%5%6%34%
1808
16th to endNight
15%8%245%3445%7%38%
1620
May1st to 15thNight
19%6%16%5%45%448%33%
1620
16th to endNight
13%5%245%25%439%43%
1661
June1st to 15thNight
9%5%245%35%45%8%46%
1440
16th to endNight
8%426%5%245%6%10%44%
1440
July1st to 15thNight
7%314435%45%7%52%
1440
16th to endNight
5%32442445%11%51%
1591
August1st to 15thNight
5%4245%35%5%5%9%48%
1620
16th to endNight
10%4235%23337%51%
1758
September1st to 15thNight
10%5%14323346%51%
1862
16th to endNight
11%4345%2445%7%46%
1815
October1st to 15thNight
14%6%25%4345%46%42%
1886
16th to endNight
20%8%35%5%24435%34%
2216
November1st to 15thNight
14%7%345%25%446%40%
2276
16th to endNight
19%11%46%5%24445%29%
2340
December1st to 15thNight
19%13%5%9%6%24436%22%
2523
16th to endNight
22%15%6%9%6%45%45%416%
2688

Percentage Cloud Cover SE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
17%16%6%10%7%45%436%17%
1432
16th to endDay
16%17%7%10%8%35%45%5%15%
1620
February1st to 15thDay
14%14%7%11%8%35%446%19%
1616
16th to endDay
15%13%6%11%8%25%347%20%
1580
March1st to 15thDay
17%12%5%7%5%3445%6%27%
1872
16th to endDay
18%9%48%6%24346%30%
2111
April1st to 15thDay
20%10%45%5%44446%30%
2148
16th to endDay
16%7%36%5%23346%38%
2340
May1st to 15thDay
18%8%36%6%35%45%6%32%
2331
16th to endDay
13%6%25%5%35%45%7%39%
2449
June1st to 15thDay
10%5%346%36%5%5%9%39%
2520
16th to endDay
9%5%25%5%47%5%8%10%34%
2520
July1st to 15thDay
7%5%34436%46%9%44%
2520
16th to endDay
7%5%25%6%45%6%7%10%39%
2577
August1st to 15thDay
8%6%25%6%45%5%6%9%39%
2340
16th to endDay
10%6%35%5%35%5%6%9%38%
2441
September1st to 15thDay
12%5%25%6%35%45%7%41%
1974
16th to endDay
11%5%35%435%5%6%8%39%
1815
October1st to 15thDay
14%6%36%6%25%45%6%38%
1744
16th to endDay
21%8%36%6%34336%31%
1653
November1st to 15thDay
14%7%46%5%3445%6%38%
1582
16th to endDay
18%12%47%6%35%446%26%
1620
December1st to 15thDay
15%14%7%10%7%35%447%20%
1422
16th to endDay
20%16%9%10%6%3334415%
1536
January1st to 15thNight
22%12%5%8%6%33445%23%
2506
16th to endNight
13%13%7%11%7%5%4446%20%
2601
February1st to 15thNight
15%14%5%8%7%35%345%26%
2235
16th to endNight
15%10%5%8%6%25%45%6%28%
1893
March1st to 15thNight
17%10%45%6%34446%32%
2088
16th to endNight
15%8%35%5%25%45%7%34%
2112
April1st to 15thNight
18%8%35%5%35%45%6%33%
1808
16th to endNight
15%8%245%3445%7%38%
1620
May1st to 15thNight
19%6%16%5%35%448%34%
1619
16th to endNight
12%5%25%5%25%348%43%
1661
June1st to 15thNight
9%4245%35%45%8%46%
1440
16th to endNight
8%326%4346%6%10%43%
1440
July1st to 15thNight
7%2145%3445%8%52%
1440
16th to endNight
442432446%9%52%
1591
August1st to 15thNight
5%415%5%35%5%6%8%48%
1620
16th to endNight
9%425%423446%51%
1758
September1st to 15thNight
11%5%14413446%51%
1862
16th to endNight
11%43443445%7%46%
1815
October1st to 15thNight
14%5%35%42445%6%42%
1886
16th to endNight
21%7%35%5%34435%34%
2216
November1st to 15thNight
14%8%25%435%35%7%40%
2276
16th to endNight
20%12%46%6%24445%29%
2340
December1st to 15thNight
19%13%6%8%6%34346%22%
2523
16th to endNight
22%15%5%9%6%45%44416%
2688

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
68%6%10%11%3
1433
16th to endDay
70%410%9%4
1620
February1st to 15thDay
65%5%9%12%5%
1618
16th to endDay
64%410%13%5%
1580
March1st to 15thDay
56%6%12%15%6%1
1872
16th to endDay
54%5%11%19%7%1
2112
April1st to 15thDay
54%410%19%10%
2148
16th to endDay
46%5%13%16%15%2
2340
May1st to 15thDay
52%6%11%18%10%1
2331
16th to endDay
43%6%12%24%11%1
2453
June1st to 15thDay
39%7%12%23%14%1
2520
16th to endDay
41%8%13%20%15%
2520
July1st to 15thDay
35%7%10%24%19%2
2371
16th to endDay
37%8%14%21%15%2
2416
August1st to 15thDay
39%7%12%24%13%1
2327
16th to endDay
40%7%11%22%15%2
2441
September1st to 15thDay
40%7%12%24%14%1
1974
16th to endDay
39%7%11%29%13%
1815
October1st to 15thDay
44%6%11%22%12%1
1744
16th to endDay
54%5%13%18%7%
1653
November1st to 15thDay
46%5%11%21%13%1
1582
16th to endDay
58%5%13%17%5%
1620
December1st to 15thDay
63%412%14%4
1422
16th to endDay
71%5%11%7%3
1536
January1st to 15thNight
62%5%10%14%6%
2506
16th to endNight
65%5%13%11%4
2601
February1st to 15thNight
60%6%10%15%5%1
2244
16th to endNight
56%313%17%7%1
1893
March1st to 15thNight
52%6%10%18%10%1
2088
16th to endNight
48%5%12%21%11%1
2112
April1st to 15thNight
49%6%10%18%14%
1808
16th to endNight
44%5%11%18%17%2
1620
May1st to 15thNight
49%5%10%20%11%2
1620
16th to endNight
38%6%12%23%15%3
1663
June1st to 15thNight
35%7%12%26%16%1
1440
16th to endNight
33%8%14%25%17%
1440
July1st to 15thNight
29%7%11%28%20%2
1360
16th to endNight
27%7%15%25%20%3
1489
August1st to 15thNight
30%7%13%30%15%2
1609
16th to endNight
33%6%11%26%19%3
1758
September1st to 15thNight
32%410%29%21%1
1862
16th to endNight
34%6%12%28%17%
1815
October1st to 15thNight
41%6%11%21%18%1
1886
16th to endNight
51%5%13%21%8%
2216
November1st to 15thNight
43%5%12%22%13%1
2276
16th to endNight
56%5%12%17%7%
2340
December1st to 15thNight
62%5%11%13%5%
2523
16th to endNight
70%5%9%9%4
2688

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
21%12%40%20%5%1
90
16th to endDay
31%10%39%14%4
96
February1st to 15thDay
24%21%41%10%3
90
16th to endDay
19%14%39%20%4
81
March1st to 15thDay
29%9%33%20%6%
162
16th to endDay
24%6%31%25%10%1
288
April1st to 15thDay
22%8%33%23%9%2
270
16th to endDay
20%9%31%18%13%7%
270
May1st to 15thDay
22%7%29%20%14%5%
288
16th to endDay
18%7%25%22%16%8%
349
June1st to 15thDay
11%5%30%30%16%5%
495
16th to endDay
10%7%33%27%16%5%
495
July1st to 15thDay
9%425%27%22%10%
475
16th to endDay
7%421%28%26%11%
437
August1st to 15thDay
10%215%28%21%21%
313
16th to endDay
13%418%20%27%16%
332
September1st to 15thDay
12%419%21%24%18%
294
16th to endDay
15%414%24%29%12%
254
October1st to 15thDay
17%423%30%17%6%
255
16th to endDay
26%9%29%26%7%
165
November1st to 15thDay
7%13%30%31%15%2
90
16th to endDay
23%17%37%14%6%
90
December1st to 15thDay
20%23%35%14%6%
64
16th to endDay
21%31%37%9%
96
January1st to 15thNight
28%12%34%18%5%
900
16th to endNight
19%11%36%26%6%
873
February1st to 15thNight
23%13%36%23%3
704
16th to endNight
21%11%33%28%4
631
March1st to 15thNight
22%12%30%26%6%
720
16th to endNight
18%10%33%27%9%1
768
April1st to 15thNight
20%12%32%27%5%
572
16th to endNight
20%6%32%28%9%1
540
May1st to 15thNight
20%5%30%32%10%1
540
16th to endNight
14%326%34%19%2
563
June1st to 15thNight
11%223%46%16%
540
16th to endNight
8%121%44%21%1
540
July1st to 15thNight
10%116%40%28%3
510
16th to endNight
4216%47%26%2
564
August1st to 15thNight
6%117%43%27%3
539
16th to endNight
11%113%34%34%5%
573
September1st to 15thNight
12%419%30%26%5%
637
16th to endNight
12%417%31%28%5%
657
October1st to 15thNight
17%5%24%32%17%2
660
16th to endNight
24%11%33%23%6%
704
November1st to 15thNight
18%9%31%25%13%1
700
16th to endNight
27%11%31%21%7%
720
December1st to 15thNight
25%13%35%21%4
753
16th to endNight
29%10%34%21%3
960
Page generated at 2017-09-11 19:35:27. Version ac04

Copyright 2017 A. Danko


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